1. Field of the Invention
The present invention relates to novel carbodiimide compounds and to novel polymers having carbodiimide-containing structural moieties as pendant groups. The invention more specifically relates to coating compositions containing said acrylic polymers suitable for use where hardening of the coating composition at low temperatures, for example, ambient temperature, is required.
2. Brief Description of Prior Art
Known coating compositions which cure at low temperatures for use as automotive quality finishes, particularly as automotive refinishing compositions, include two-package compositions based on hydroxy-functional components and curing (crosslinking) agents containing isocyanate groups. However, the use of isocyanate functional materials often requires that precautions be taken with respect to the handling and use of the isocyanates based on toxicity considerations. Such precautions can be relatively burdensome particularly when the coating compositions are utilized in environments not involving controlled factory conditions as exist, for example, in plants producing new automotive vehicles. For example, the application of automotive refinishing compositions tends to be done in refinishing shops under conditions which are not nearly as well controlled as those existing in automotive plants which manufacture original equipment. Accordingly, there is a need for high quality coating compositions which are not based on the utilization of isocyanate curing agents.
The present invention addresses these issues. The novel acrylic polymers bearing the pendant carbodiimide functional groups described and claimed in the present invention have been found to be useful in ambient temperature cured coatings.
Hamon in U.S. Pat. No. 4,612,054, as well as the references in said patent, teach the benefits of carbodiimides in many applications, including coatings. None of these discloses, or even suggests, the existence of an ethylenically-unsaturated carbodiimide monomer which can be readily incorporated into an acrylic backbone to form polycarbodiimides that are useful in producing coating compositions, for example, for refinishing automobiles. While the carbodiimides disclosed for use by Hamon can be symmetrical or asymmetrical, the novel carbodiimides disclosed and claimed herein can not be symmetrical. Moreover, there is no teaching or any suggestion whatsoever that the substituents attached to the carbodiimide used by Hamon can be ethylenically unsaturated, as required herein. In fact, there is no reason why Hamon would wish to suggest the use therein of a carbodiimide containing an ethylenically unsaturated substituent.
Watson, Jr., in U.S. Pat. No. 4,977,219, Godbey, Jr. et al., in U.S. Pat. No. 4,966,948 and Henning et al. in U.S. Pat. No. 4,910,339 neither disclose nor teach the production of a carbodiimide containing an ethylenically unsaturated substituent nor an acrylic polymer containing pendant carbodiimide moieties.